Filter for liquids

Abstract

Filter for liquids comprising a casing (100) with a lower cover (30) and an upper cover (4), and a filtering element (9), coaxially fitted into the casing (1) and having an enlarged annular base (10). The lower cover (30) has an outer axial wall (31) and an inner axial wall (32) defining an intermediate annular cavity (33) into which there is engaged an enlarged lower portion (34) of the side wall (2) of the casing (100). The enlarged annular base (10) of the filtering element (9) is relatively soft and it is sealingly engaged with radial interference into the enlarged lower portion (34) of the side wall (2) of the casing (100), and it is also axially locked between an inner annular step (35) of the side wall (2) of the casing (100) and the inner axial wall (32) of the lower cover (30).

Description

[0001] "Filter for liquids"

[0002] Field of the invention

[0003] The present invention relates to filters for liquids , in particular subj ected to positive and negative pressure through the filter .

[0004] More in particular, the invention relates to a filter comprising a casing with an axially elongated cylindrical side wall having a lower cover with an inlet / outlet tubular fitting, and an upper cover with an outlet / inlet tubular fitting . A filtering element is coaxially fitted into the casing and it has an annular base sealingly fixed into the casing .

[0005] State of the prior art

[0006] When using filters thus made , the liquid, for example blood, flows in from the tubular fitting of the lower cover, it flows through the filtering mesh wall of the filtering element and flows out from the tubular fitting of the upper cover and then delivered to a treatment equipment . Once through with the treatment , the blood is del ivered again to the patient flowing in from the tubular fitting of the upper cover, flowing through the filtering element and flows out from the filter through the tubular fitting of the upper cover . Therefore , the blood may flow pressurised from inside the filtering element towards the external , or from outside the filtering element towards the internal . It is essential to avoid the occurrence by-pass events between the internal and the external of the filtering element : the blood must always flow through the wall of the filtering element , typically consisting of a comoulded mesh with the annular base and with sti f fening parts .

[0007] A prior art filter thus made wil l now be described with reference to figures 1 and 2 of the attached drawings .

[0008] The filter comprises a flexible or sti f f casing 1 ( or drip chamber ) having an axially elongated cylindrical side wall 2 closed at the ends thereof respectively by a lower cover 3 and by an upper cover 4 . The expressions " lower" and "upper" refer to a configuration of normal use of the filter arranged in a fluid line , for example for blood, between a patient and a treatment equipment .

[0009] The lower cover 3 is provided with an inlet / outlet tubular fitting 5 and similarly the upper cover 4 is provided with an outlet / inlet tubular fitting 6 . As better observable in figure 2 the lower cover 3 has a radial flange 7 which frontally counteracts against the lower end of the side wall 2 of the casing 1 , and an axial tang 8 engaged and glued against the inner surface of the lower part of the side wall 2 .

[0010] Inside the casing 1 there is coaxially fitted a filtering element 9 having at the lower part a sti f f annular base 10 with which there are co-moulded a tubular mesh or a filtering microperforated wall 11 , an axial sti f fening rod 12 and an upper closing wall 13 .

[0011] In use , the blood coming from the patient flows into the filter 1 through the fitting 5 , which is the inlet fitting in this case , penetrates into the filtering element 9 , it flows through the fi ltering mesh 11 thereof towards the side wall 2 of the casing 1 and then therefore flows out from the tubular fitting 6 , which forms the outlet fitting in this case . With the reverse flow, the blood returns into the filter 1 flowing in from the tubular fitting 6 , which is the inlet fitting in this case , through the filtering mesh 11 penetrating into the filtering element 9 and flowing out through the tubular fitting 5 , which forms the outlet fitting in this case .

[0012] As already clari fied above it is essential that the fluid always flows through the filtering mesh 11 , without the possibility of a direct by-pass between the two tubular fittings 5 , 6 . Therefore , the annular base 10 of the filtering element 9 must be sealingly fixed both to the wall 2 of the casing 1 , and to the lower cover 3 : to this end, according to the prior art , the sti f f annular base 10 is laterally glued to the wall 2 , and frontally to the tang 8 of the lower cover 3 , which is in turn glued to the inner surface of the side wall 2 of the casing 1 . Therefore , the manufacturing of the prior art filter requires carrying out three gluing operations , with the relative manufacturing complication .

[0013] Document US 3685659 describes a filter having an end fitted with axial clearance between the outer and inner axial walls of a cover . In order to obtain the airtight seal of the filter with respect to the cover, there are provided for a first and a second radial annular seal .

[0014] Summary of the invention

[0015] The obj ect of the invention is to simpli fy the filter, in particular reducing the number of gluing operations required to ensure the perfect sealing between the annular base of the filtering element and the casing of the filter, and also avoid the need to provide for auxiliary airtight seal gaskets .

[0016] According to the invention, this obj ect is attained thanks to the characteristics mainly defined in the characterising part of claim 1 .

[0017] Thanks to such characteristics , the gluing operations required for manufacturing the filter are basically reduced to j ust one , that is the one between the enlarged lower portion of the side wall of the casing and the annular cavity of the lower cover, while the sealing retention of the annular base of the filtering element is obtained mechanically, without the need for gluing operations and auxiliary seals , on the one hand due to the elasticity thereof which provides the radial interference thereof against the s ide wall of the casing and on the other hand due to the front locking against the inner axial wall of the lower cover . The presence of the outer axial wall of the lower cover exerts an action for radially containing the lower portion of the side wall of the casing against which there abuts the annular base of the filtering element , preventing such wall from deforming, that is widening radially, allowing an unwanted by-pass between the two tubular fittings of the filter .

[0018] According to a preferred embodiment of the invention both the inner axial wall and the outer axial wall of the cover are internally formed with axial sti f fening ribs .

[0019] Brief description of the drawings

[0020] The invention wil l now be described in detail with reference to attached drawings , wherein :

[0021] - figure 1 is an axial cross-sectional perspective view of a filter according to the prior art , described above ,

[0022] - figure 2 shows an enlarged scale of the detail of figure 1 ,

[0023] - figure 3 is a schematic perspective view of a filter for liquids according to the invention, figure 4 is an axial cross-sectional view of figure 3 ,

[0024] - figure 5 is a partial exploded perspective view of the filter,

[0025] - figure 6 shows - in a larger scale - a detail of figure 4 , and figures 7 and 8 are two cross-sectional perspective views and in larger scale of the detail of figure 6 which exempli fy the assembly of the filter .

[0026] Detailed description of the invention

[0027] Referring to figures 3 to 8 , the filter according to the invention comprises various components similar to those already described above with reference to the filter according to the prior art shown in figures 1 and 2 and indicated using the same reference numerals .

[0028] The filter according to the invention comprises a casing 100 with an elongated generally cylindrical side wall 2 , having a lower cover 30 with an inlet / outlet tubular fitting 5 , and an upper cover 4 , with one or two outlet / inlet tubular fitting 6 .

[0029] In the casing 100 there is coaxially fitted a generally cylindrical filtering element 9 , formed by a co-moulded annular base 10 with a tubular mesh with micro-holes 11 , as well as axial and radial sti f fening elements 12 , and by an airtight sealing upper cover 13 .

[0030] The annular base 10 is enlarged, in the sense that it has a diameter larger than that of the tubular mesh 11 , and it is made of a relatively soft and elastic material , for example silicone rubber .

[0031] According to the peculiar feature of the invention, the lower cover 30 has , made as a single piece , an outer axial wall 31 and an inner axial wall 32 , radially spaced from each other so as to define an intermediate annular cavity 33 . The side wall 2 of the casing 100 is formed at the lower part with an enlarged portion 34 which is axially fitted and sealingly fixed, for example by gluing, into the annular cavity 33 . Such enlarged lower portion 34 defines , with the upper part of the wall 2 of the casing 100 , an inner annular step 35 facing the upper edge of the inner annular wall 32 of the lower cover 30 .

[0032] The sealed fixing of the filtering element 9 relatively to the lower cover 30 is obtained without the need for gluing operations , due to the fact that the annular base 10 is forcedly fitted with sealing elastic radial interference into the enlarged portion 34 of the wall 2 of the casing 100 , and it is also axially locked between the inner annular step 35 and the inner axial wall 32 of the lower cover 30 . Due to the relatively soft conformation thereof the annular base 10 therefore provides the required airtight seal without the need for auxiliary seals .

[0033] Figures 7 and 8 show assembling of the filter according to the invention : firstly, the filtering element 9 is introduced axially from the bottom into the casing 100 , open at the lower part , until it abuts the annular base 10 against the step 35 and with radial interference relatively to the enlarged portion 34 of the casing 100 ( figure 7 ) . Therefore , the casing 100 and the lower cap 30 are assembled to each other by fitting the enlarged portion 34 of the wall 2 into the cavity 33 , until the annular base 10 is arranged frontally abutting against the top part of the inner axial wall 32 ( figure 8 ) . The annular base 10 is therefore firmly sealingly locked between the inner axial wall 32 of the lower cap 30 and the annular step 35 of the wall 2 of the casing 100 , radially pressing against the part of the enlarged portion 34 of the wall 2 which protrudes from the cavity 33 . The outer axial wall 31 of the cover 30 prevents , in use , due to the pressure inside the filter, the enlarged lower portion 34 of the wall 2 from being deformed radially toward the external causing leakage that could allow an unwanted direct by-pass communication between the tubular fittings 5 and 6 .

[0034] The outer axial wall 31 and / or the inner axial wall 32 of the lower cover 30 can be conveniently formed internally with axial sti f fening ribs 36 , 37 . In the light of the above it will be clear that the filter according to the invention may be manufactured in a signi ficantly simpler and more cost-ef fective manner with respect to the conventional filters , essentially due to the fact that the assembl ing thereof at most requires a single gluing operation, instead of multiple gluing operations .

[0035] Obviously, without prej udice to the principle of the invention, the construction details and the embodiments may widely vary with respect to what has been described and illustrated, without departing from the scope of protection of the present invention as defined in the claims that follow .

Claims

CLAIMS1. Filter for liquids, comprising a casing (100) with an axially elongated cylindrical side wall (2) having a lower cover (30) with an inlet / outlet tubular fitting (5) and an upper cover (4) with an outlet / inlet tubular fitting (6) , and a filter element (9) inserted coaxially into the casing (100) and having an annular base (10) sealingly fixed to the lower cover (30) and to the side wall (2) of the casing (100) , characterised in that :- the lower cover (30) has an outer axial wall (31) and an inner axial wall (32) , spaced radially from the outer wall (31) and defining an intermediate annular cavity (33) therewith,- the side wall (2) of the casing (100) has an enlarged lower portion (34) which is fitted and sealingly fixed into said annular cavity (33) and defines an inner annular step (35) facing said inner axial wall (32) of the lower cover (30) ,- said annular base (10) of the filtering element (9) is enlarged and relatively soft and it is sealingly engaged with radial interference within said enlarged lower portion (34) of the side wall (2) of the casing (100) and it is also locked axially between said inner annular step (35) and said inner axial wall (32) of the lower cover (30) .

2. Filter according to claim 1, characterised in that said inner axial wall (32) of the lower cover (30) is internally formed with axial stiffening ribs (37) .

3. Filter according to claim 1 or claim 2, characterised in that said outer axial wall (31) of the lower cover (30) is internally formed with axial stiffening ribs (36) .

Images